We are concerned with examining the presence and modulation of epsilon-(gamma-glutamyl) lysine bonds in proteins of procaryotic and eucaryotic cells. We have shown that glu-lys bonds are present in the proteins of a wide variety of cells. We are able to modulate their frequency by exposing preparations to such agents as Mg ions ATP and Ca ions. We are also in the process of identifying the protein chains which are crosslinked by glu-lys bonds and hope to identify the cellular processes involved in the modulation of these bonds. We are developing more rapid analytical procedures which can identify the protein chains acting as substrates for enzymes involved in crosslink formation and crosslink breaking.